基于双模谐振器的双通带可调谐滤波器设计

从理论上分析了开路支节加载双频谐振器的谐振模式,通过在谐振器末端加载变容二极管的方式,设计了一款双通带独立可调谐滤波器。通过调节谐振器末端变容二极管电容值大小来改变通带的中心频率,通过调节支节末端的变容二极管来调节通带的带宽。该滤波器的两个通带之间相互独立,调谐其中一个通带对另一个通带几乎没有影响。通过引入源与负载的耦合,使得双通带两侧各产生一个传输零点,提高了滤波器的选择性和带外抑制能力。最终设计出的滤波器第一通带的中心频率在1.08~1.19 GHz之间连续可调,绝对带宽在112~152 MHz之间连续可调;第二通带中心频率在2.07~2.22 GHz 之间连续可调,其绝对带宽在132~189 MHz 之间连续可调。在调谐过程中,通过调节中心开路支节末端变容二极管加载直流电压大小,实现调谐过程两通带带宽基本维持不变。

Design of Tunable Dualband Bandpass Filter Based on Dual-Mode Resonator

In this paper, we theoretically analyze the resonant modes of the dual-band resonator loaded with open branches and design a two-pass band independently tunable filter by loading varactor at the end of the resonator. The center frequency of the passband is changed by adjusting the capacitance value of the varactor at the end of the resonator. The pass-band bandwidth is adjusted by adjusting the varactor at the end of the open branch. The two passbands of the filter are independent of each other, and when we adjust one of the passbands, it has little effect on another passeband. By introducing the coupling of the source and the load, we have a zero-point of transmission on each side of the each passband, which improves the selectivity and out-of-band rejection of the filter. The performance of the final designed filter: the center frequency of first passband can be continuously adjusted between 1.08 GHz and 1.19 GHz, its absolute bandwidth can be continuously adjusted between 112 MHz and 152 MHz; The center frequency of second passband can be continuously adjusted between 2.07 GHz and 2.22 GHz, Its absolute bandwidth can be continuously adjusted between 132 MHz and 189 MHz. During the tuning process, by adjusting the DC voltage of varactors at the ends of open branches in the center, the bandwidth of two passbands can remain virtually unchanged.